[systemd-devel] [PATCH v4 3/3] udev: input_id - use ABS_MT_SLOT{-1} to exclude non touch screen devices

[Andreas Pokorny]

Peek at the ABS_MT_SLOT-1 axis. Expect that touch screens only
have axes inside the MT range.
---
 src/udev/udev-builtin-input_id.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/udev/udev-builtin-input_id.c b/src/udev/udev-builtin-input_id.c
index 0f9f021..59616c8 100644
--- a/src/udev/udev-builtin-input_id.c
+++ b/src/udev/udev-builtin-input_id.c
@@ -170,7 +170,8 @@ static bool test_pointers(struct udev_device *dev,
         finger_but_no_pen = test_bit(BTN_TOOL_FINGER, bitmask_key) && !test_bit(BTN_TOOL_PEN, bitmask_key);
         has_mouse_button = test_bit(BTN_LEFT, bitmask_key);
         has_rel_coordinates = test_bit(EV_REL, bitmask_ev) && test_bit(REL_X, bitmask_rel) && test_bit(REL_Y, bitmask_rel);
-        has_mt_coordinates = test_bit(ABS_MT_POSITION_X, bitmask_abs) && test_bit(ABS_MT_POSITION_Y, bitmask_abs);
+        has_mt_coordinates = test_bit(ABS_MT_POSITION_X, bitmask_abs) && test_bit(ABS_MT_POSITION_Y, bitmask_abs) &&
+                             test_bit(ABS_MT_SLOT, bitmask_abs) && !test_bit(ABS_MT_SLOT - 1, bitmask_abs);
         is_direct = test_bit(INPUT_PROP_DIRECT, bitmask_props);
         has_touch = test_bit(BTN_TOUCH, bitmask_key);
         /* joysticks don't necessarily have buttons; e. g.
-- 
2.1.4